Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$43.33	4.587%	$45.3175	$45.32	$45.30	$45.30
Purchase #2	$116.83	4.814%	$122.4542	$122.45	$122.45	$122.50
Purchase #3	$54.81	12.209%	$61.5018	$61.50	$61.50	$61.50
Purchase #4	$198.47	10.415%	$219.1407	$219.14	$219.15	$219.10
Purchase #5	$196.47	9.513%	$215.1602	$215.16	$215.15	$215.20
Purchase #6	$203.47	7.555%	$218.8422	$218.84	$218.85	$218.80
Purchase #7	$158.81	8.201%	$171.834	$171.83	$171.85	$171.80
7 purchase totals =	$972.19		$1,054.2506	$1,054.24	$1,054.25	$1,054.20